The present invention relates a paper cassette and a printer for use with the paper cassette. The present invention relates also to a method of supplying recording sheets from the paper cassette to the printer.
Among printers, thermal printers are classified into thermosensitive printers and thermal transfer printers, each of these two types uses a specific kind of recording paper. Recording paper for the thermosensitive printer has a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, and a yellow thermosensitive coloring layer formed sequentially atop another on a base material. The thermosensitive coloring layers are subjected to thermal recording sequentially from the obverse side, while being optically fixed before the next thermosensitive coloring layer is subjected to the thermal recording. The optical fixing is disabling coloring-capability of the individual thermosensitive coloring layer by exposing it to electromagnetic rays of a specific wavelength range, e.g. ultraviolet rays, that is determined for each thermosensitive coloring layer, so that already colored thermosensitive coloring layers will not be re-colored by the thermal recording on the next thermosensitive coloring layer. Because coloring characteristics of the recording paper for the thermosensitive printer are affected even by light from ordinary light sources if the recording paper is exposed for a long time, the recording paper is preserved in a light-tight bag, and the light-tight bags are encased in a paper box when the recording paper is shipped out of factory.
On the other hand, the thermal transfer printers are classified into a melting type where ink is melted or softened to be transferred from ink film onto the recording paper, and a sublimation type where dyes on an ink film are transferred onto the recording paper by sublimation or dispersion. For the melting type printer, a high-smooth coated paper is used as the recording paper. For the sublimation type printer, a specific paper coated with polyester resin is used as the recording paper. The recording paper for these thermal transfer printers is contained in a moisture-proof bag, and the bags are contained in a paper box at the shipment.
To load the recording sheets in a printer, first the bag is opened to take out. There is a recording sheet package that contain a stack of sheets of recording paper, and the recording sheet package is loaded in a paper cassette. Then, the paper cassette is placed in the printer, so the recording sheet is fed from the paper cassette into the printer. The paper cassette has an air-proof sponge or the like along a mating portion between a cassette body and a lid, for protecting the contained recording sheets from moisture, as disclosed for example in JPA 9-132330.
Although the above mentioned paper cassette is completely closed in its preservative condition where the lid is closed, but the lid must be opened for paper-feeding, then the moisture-shielding properties of the cassette decreases. Moreover, where the recording sheets are to be fed out from a stack, a trouble of feeding a plurality of recording sheets along with an uppermost one, called multi-feeding, is likely to occur. This trouble can occur at any kinds of recording sheets, including thermosensitive recording sheets.
As a result of multi-feeding, the recording sheets may jam up in a paper feeding path, or recording area on the recording sheet may be deviated. As a result of multi-feeding, leading ends of the multi-fed recording sheets may be left protruded from the paper cassette. Since recording surfaces of the recording sheets are protected from moisture and light by stacking the recording sheets in tight contact with each other, if the recording sheets are left protruded for a long time, coloring characteristics of the recording surfaces of the protruded recording sheets are affected by moisture and light. A change in the coloring characteristics results in undesirable variations in color or density of the recorded image.
The recording sheets can also protrude from a paper supply start position in the paper cassette or in the printer when the paper cassette or the printer with the paper cassette attached thereto is carried about. Also while the paper cassette is being attached to the printer, the recording sheets can protrude from the paper supply start position. If the recording sheets are in this condition at the start of paper feeding, it may cause multi-feeding, and jamming of the recording sheets are likely to occur. The same applies not only to the thermal printers but also to any other kinds of printers.
An object of the present invention is to provide a paper cassette, a printer and a paper feeding method, that prevent multi-feeding and keep protecting the recording surface of the recording sheet from moisture and light.
In a printer supplied with recording sheets one by one from a paper cassette by rotating paper supply rollers, the paper cassette being loaded with a stack of recording sheets, the present invention is characterized by comprising a paper supply roller control device that executes a paper supply mode and a returning mode, wherein the paper supply roller control device causes the paper supply rollers to rotate in a first direction in the paper supply mode, to feed an uppermost or a lowermost one of the recording sheets into the printer, or causes the paper supply rollers to rotate in a second direction in the returning mode, to return the recording sheet to a predetermined paper supply start position inside the paper cassette.
The returning mode is executed after an end of paper supply, when a power source of the printer is turned on, or when the paper cassette is loaded in the printer.
The paper supply mode is executed in response to a print start command. At that time, it is possible to execute the returning mode immediately before the paper supply mode. In that case, the paper supply rollers are rotated in the second direction to return the recording sheets to the predetermined paper supply start position inside the paper cassette before the paper supply rollers are rotated in the first direction to feed the uppermost or the lowermost recording sheet into the printer.
Even if the recording sheets are deviated from the predetermined paper supply start position because of multi-feeding or other reasons, these recording sheets are returned to the initial position, so that occurrence of multi-feeding and jamming of the recording sheets in the next paper supply mode is reduced. Beside that, the recording sheets are kept shielded from moisture and light.
A paper cassette according to the present invention comprises a cassette body loaded with a stack of recording sheets and having a parallelepiped shape with an open end that serves as a paper supply opening; paper supply rollers located in proximity to the paper supply opening of the cassette body in contact with a first one of the recording sheets that is placed at the uppermost or the lowermost position of the stack, the paper supply rollers being rotated to feed the recording sheet out of the cassette body; a recording sheet urging member that pushes the entire stack of the recording sheets to press the first recording sheet onto the paper supply rollers; and a recording sheet separator for separating the first recording sheet from a second and following recording sheets, the recording sheet separator being located in the paper supply opening and movable between a paper separating position where the recording sheet separator is in contact with leading ends of the second following recording sheets, and an open position away from the leading ends of the recording sheets to open the paper supply opening, wherein the first recording sheet is fed out from the cassette body through a paper passageway that is formed between the recording sheet separator and the paper supply opening while the recording sheet separator is in the paper separating position.
According to the present invention, the recording sheets are loaded in the cassette body that has only one end open as the paper supply opening, and the paper supply opening is also closed by the recording sheet separator such that the narrow paper passageway is left unclosed. Because the paper passageway is shielded when the paper cassette is placed in the printer, the paper cassette of the present invention is improved in light- and moisture-shielding properties.
Since the recording sheet separator is movable between the paper separating position where the recording sheet separator is in contact with the leading ends of the second and following recording sheets, and the open position retracted from the paper supply opening, the recording sheet separator in the paper separating position can separate the recording sheets from each other during the paper feeding, thereby preventing multi-feeding. On the other hand, in the retracted position, the recording sheet separator is retracted from the paper supply opening to open up the paper supply opening, so the recording sheets may be loaded through the paper supply opening into the cassette.
The light- and moisture-shielding properties are still more improved by providing the light-shielding member, which is made of a resilient plate bent into a wavy shape, in the paper passageway, such that the bent portions of the resilient plate are in contact with the recording sheet separator to close the paper passageway. The recording sheet passes through the paper passageway while being pressed gently by the bent portions against the recording sheet separator.
Incorporating the paper supply rollers into the paper cassette makes it unnecessary to provide roller openings that allows the paper supply rollers to enter the paper cassette, and thus provides improved light- and moisture-shielding properties. Where the paper supply rollers are not incorporated into the paper cassette, the sliding lid member is mounted to the roller opening, and is urged by a coiled spring to the closed position, so the roller opening is closed while the paper cassette is not attached to the printer. Thereby, the paper cassette is maintained light-tight and moisture-tight.